JPH0764008B2 - Method for producing polypropylene resin sheet or film - Google Patents

Abstract

The present invention relates to a process for producing a polypropylene resin sheet or film which comprises introducing a polypropylene resin in a film form, which has been extruded from a T-die in a molten state, into a slit through which a cooling water is flowing, passing the polypropylene resin film between nip rolls, and pressing the above obtained sheet or film from both sides thereof under a pressure of at least 5 kg/cm<2> while heating at a temperature of 155 to 160 DEG C, by the use of a metal belt having a surface roughness of not more than 0.1 mu m. In accordance with the present invention, a sheet or film of a polypropylene resin which is unstretched and is excellent in transparency and surface gloss can be obtained. Furthermore, the sheet or film obtained is good in transparency and surface gloss even when it is thick. In accordance with the present invention, even if the film-forming speed is high, a sheet or film having excellent transparency can be obtained. Furthermore, in the sheet or film obtained, gel and fish eye are not prominent, and the sheet or film is excellent in heat moldability. <IMAGE>

Description

The present invention relates to a method for producing an ultra-high transparent unstretched polypropylene resin sheet or film suitable for packaging foods, pharmaceuticals and the like.

[Problems to be Solved by Prior Art and Invention]

Conventionally, a sheet or film made of a crystalline thermoplastic resin, particularly a polypropylene resin, has different physical properties such as transparency depending on its crystal form.

The present applicant has proposed various crystallization control techniques by rapid cooling as a method for improving the transparency of a crystalline thermoplastic resin sheet or film (Japanese Patent Publication No. 62-41457,
62-10816, JP-A-62-42822, and 60-23.
6719 publication), and has already been put to practical use.

However, in recent years, further improvement in quality and productivity of sheet products have been demanded.

By the way, in the case of the above-mentioned conventional method, for example, in the case of a 0.2 mm thick sheet, the film forming speed is 20 m / min. Or more, particularly 30 m / mi.
When the speed is higher than n., the transparency gradually decreases. It is considered that this is due to the sharkskin on the surface of the sheet due to an increase in die shear stress.

Therefore, from the viewpoint of improving productivity, the film forming speed is 20 m /
There is a demand for a sheet or film that does not decrease in transparency even at a speed of min. or more, particularly 30 m / min. or more.

Further, in the case of the above conventional method, when the thickness of the sheet is 0.6 mm or more, due to the heat transfer limit in the thickness direction,
There was also a problem that the transparency dropped sharply.

Therefore, a highly transparent sheet is required even if it is thick.

On the other hand, other technologies proposed in addition to the above conventional method,
For example, the roll method and the method of adding a nucleating agent have a drawback that the transparency itself is inferior as a problem before the film forming speed and the thickness of the sheet.

It is an object of the present invention to solve the above-mentioned conventional problems and to provide a method for producing a sheet or film having excellent transparency and gloss even with a thick wall with high productivity.

[Means for Solving the Problems]

That is, the present invention introduces a film-shaped polypropylene resin extruded in a molten state from a T-die into a slit through which cooling water flows and heats a sheet or film obtained through a pinching roll to 155 to 160 ° C. , 5 to 30 on both sides of the sheet or film with a metal belt having a surface roughness of 0.1 μm or less
The present invention provides a method for producing a polypropylene resin sheet or film, which comprises pinching at a pressure of kg / cm ² .

In the present invention, as the polypropylene resin used as a raw material for the sheet or film, a propylene homopolymer, one or more crystalline propylene-based copolymers, and a mixture thereof can be used.

The sheet or film of the present invention also includes a multilayer sheet or film. Further, although the present invention basically does not require these, if necessary, nucleation of silica, talc, paratertiary butyl benzoic acid, aluminum, dibenzylidene sorbitol, fine powder of high melting point resin, etc. It also includes those to which agents, petroleum resins, terpene resins, coumarone resins, etc. have been added, and propylene raw materials that have been heat treated with organic peroxides.

Hereinafter, the method of the present invention will be described with reference to the drawings.

FIG. 1 is an explanatory view showing one mode of an apparatus for carrying out the method of the present invention.

First, a film-shaped polypropylene resin 2 extruded in a molten state from a T-die 1 is introduced into a slit 3 in which cooling water flows.

This slit 3 is formed by connecting to an upper water tank 4 located below the T-die 1, and usually has a length of 5 to 100 m.
Although the size is m, the shorter one is preferable. In the upper water tank 4, it is necessary that the water in the introduction portion of the film-shaped polypropylene resin 2 flows, and the water level should be as low as possible. Generally, 7 mm or less is preferable. Here, if the water level exceeds 7 mm, boiling unevenness, haze unevenness, and curl occur in the obtained sheet, and the total haze also becomes 25 to 28%, which is not preferable.

Since the cooling water flows from the water tank 4, the film-shaped polypropylene resin 2 is cooled by the cooling water when passing through the slit 3.

That is, the cooling water flows in parallel on both sides of the film-shaped polypropylene resin 2 and is efficiently cooled.

It is desirable that the flow rate of this cooling water be close to the traveling speed of the film-shaped polypropylene resin 2.

If necessary, two or more multi-stage slits can be used. In this case, it is not always necessary to give special consideration to the adjustment of the water level and the like for the slits of the second and subsequent stages.

Next, the film-shaped polypropylene resin 2 thus cooled is sent to the lower water tank 5 and passed through the pinching rolls 6 to form a sheet or film. Here, the thickness of the sheet or film is preferably 0.5 mm or less.
If the thickness of the sheet or film exceeds 0.5 mm, the internal haze is deteriorated, which is not preferable.

That is, as shown in the figure, the lower water tank 5 is usually provided with a semi-immersive pinching roll 6 in which the lower part of the roll is submerged in water. Before the cooling water flowing inside forms a turbulent flow, it is used to press the film-shaped polypropylene resin 2 and transfer the mirror surface of the roll.

The film-shaped polypropylene resin 2 that has passed through the semi-immersion type pressure roll 6 is cooled by cooling water in the lower water tank 5,
It is taken up by the take-up roll 7.

The temperature of the cooling water is preferably low, preferably 10 ° C. or lower, and an aqueous solution containing calcium chloride or the like may be used if necessary.

In this way, it is preferable to manufacture a sheet or film having as good an internal haze as possible.

Next, while heating the polypropylene resin sheet or film 8 thus taken up by the take-up roll 7, both sides of the polypropylene resin sheet or film 8 are clamped by the metal belt 9 while being heated.

More specifically, as shown in the figure, both sides of the polypropylene resin sheet or film 8 are heated and pressed using a pair of metal belts 9 heated by a heating roll 10.
By this heating and pinching treatment, high gloss is imparted to the sheet surface. Particularly, in the present invention, since the heating and pinching treatment is performed by surface contact using the pair of metal belts 9 heated by the heating rolls 10, an excellent product can be obtained.

As the metal belt 9, a metal belt having a surface roughness of 0.1 μm or less, preferably 0.02 μm or less, which is mirror-finished is used.

The metal belt 9 is usually made of SUS, carbon steel, titanium alloy, preferably SUS.

Further, as the metal belt 9, an endless belt having a thickness of about 0.8 mm is usually used. Such an endless metal belt 9 is usually 18 to 36 m / min.
It is driven at a relatively high speed.

For clamping the both surfaces of the polypropylene resin sheet or film 8 by the metal belt 9, specifically, a hydraulic press 11 as shown in the figure is usually used, but a roller press may be used if necessary. .

The pressing pressure at the time of this clamping is 5 to 30 kg / cm ² , preferably 10 to 30 kg / cm ² . If the pressing pressure is less than 5 kg / cm ² , a sheet or film excellent in transparency and surface gloss cannot be obtained.

The pinching is performed while heating the polypropylene resin sheet or film 8 through the heating roll 10 by the metal belt 9 to 155 to 160 ° C.

If the temperature of the polypropylene resin sheet or film 8 is lower than 155 ° C, it is impossible to obtain a sheet or film excellent in transparency and surface gloss.

On the other hand, if the temperature of the polypropylene resin sheet or film 8 exceeds 160 ° C., the sheet or film may be fused to the metal belt 9, which is not preferable.

The polypropylene resin sheet or film 8 which has been subjected to the pressing treatment in this way is usually cooled by using a cooling roll 12.

After cooling, the product is wound on a winding roll to obtain a product, but it is preferable to perform heat treatment (annealing) using a heating roll or the like at the stage before the winding from the viewpoint of preventing curling. The heating temperature in this case is 80-130 ℃,
It is preferably 110 to 130 ° C.

The above description is for a single-layer sheet or film, but it is also possible to make a thick laminated sheet by using the apparatus shown in FIG.

That is, separately, a sheet or film that has been subjected to a cooling treatment by the water cooling method as described above, or is subjected to a cooling treatment by the water cooling method as described above in advance, and is wound up on a feeding device (feeding portion of the laminate raw fabric) 13. The sheet or film 14 which is present, is superposed on the polypropylene resin sheet or film 8 which has been taken up by the take-up roll 7 as described above, and the transparency is obtained in the same manner as described below using the apparatus shown in FIG. An excellent polypropylene resin laminate can be manufactured.

〔Example〕

 Next, examples of the present invention will be described.

Example 1 A polypropylene resin sheet was manufactured using the apparatus shown in FIG.

Polypropylene resin (density 0.91g / cm ³ , melt index 2.0g / 10min, Idemitsu Polypro F / 200S) resin temperature 280 ℃
Then, it was extruded using a T-die extruder (extruder diameter 120 mm, L / D = 28, die width 500 mm, die lip interval 1 mm).

The extruded molten resin film 2 is provided with slits 3 through which cooling water flows.
(Width 3 mm), and then passed through a semi-immersive pinching roll 6 (diameter 80 mm) provided in the lower water tank 5, then the lower water tank 5
It was cooled with the cooling water inside and taken up by the take-up roll 7.

Next, a pair of metal belts 9 (made of SUS, endless belt, surface roughness 0.0) heated to a predetermined temperature by the heating roll 10.
Table 1 shows the temperature of the heating roll 10 at 1 μm, the belt thickness of 0.8 mm. The temperature of the cooling roll 12 was 40 ° C. ), The both sides of the polypropylene resin sheet or film 8 are clamped by the pressure shown in Table 1 (using a hydraulic press 11).
Then, a polypropylene resin sheet was obtained.

The operating conditions and the results are shown in Table 1.

Example 2 A sheet having a thickness of 0.6 m was prepared in the same manner as in Example 1 except that the apparatus shown in FIG. 2 was used and the conditions shown in Table 1 were used.
A 2-layer polypropylene resin laminate sheet of m (0.3 mm × 2 sheets) was obtained. The operating conditions and the results are shown in Table 1.

Example 3 A sheet having a sheet thickness of 0.1 was prepared in the same manner as in Example 2 except that two feeding devices 13 were used and the conditions were as shown in Table 1.
A 9 mm (0.3 mm × 3) 3-layer polypropylene resin laminate sheet was obtained. The operating conditions and the results are shown in Table 1.

Comparative Example 1 In Example 1, instead of the pinching treatment by the metal belt 9, an annealing treatment (120 ° C. roll annealing) was performed.
A polypropylene resin sheet having a sheet thickness of 0.3 mm was obtained in the same manner as in Example 1 except that the above was performed. The operating conditions and the results are shown in Table 1.

Comparative Example 2 In Example 1, instead of the pinching treatment with the metal belt 9, an annealing treatment (120 ° C. roll annealing) was performed.
A polypropylene resin sheet having a sheet thickness of 0.6 mm was obtained in the same manner as in Example 1 except that the line speed was set to 15 m / min. The operating conditions and the results are shown in Table 1.

Example 4 In Example 1, except that the pressing treatment with the metal belt 9 was followed by the annealing treatment (120 ° C. roll annealing) and under the conditions shown in Table 1.
A polypropylene resin sheet having a sheet thickness of 0.6 mm was obtained in the same manner as in Example 1. The operating conditions and the results are shown in Table 1.

Comparative Example 3 The same procedure as in Example 1 was repeated except that the molten resin film was extruded under the same raw material and extrusion conditions as in Example 1, air was blown onto the mirror-finished roll with an air knife, and the line speed was set to 30 m / min. A polypropylene resin sheet having a sheet thickness of 0.3 mm was obtained. The operating conditions and the results are shown in Table 1.

Comparative Example 4 The molten resin film was extruded under the same raw material and extrusion conditions as in Example 1, air was blown onto the mirror-finished roll with an air knife, and then nipping was performed by the metal belt 9 in the same manner as in Example 1, and A polypropylene resin sheet having a sheet thickness of 0.3 mm was obtained in the same manner as in Example 1 except that the conditions shown in Table 1 were used. The operating conditions and the results are shown in Table 1.

Comparative Example 5 Sheet thickness was the same as in Example 1 except that the molten resin film was extruded under the same raw material and extrusion conditions as in Example 1, quenched using a touch roll, and the line speed was 8 m / min. 0.6 m
A polypropylene resin sheet of m was obtained. The operating conditions and the results are shown in Table 1.

Comparative Example 6 A sheet having a thickness of 0.3 m was prepared in the same manner as in Example 1 except that the temperature of the heating roll 10 was 120 ° C.
A polypropylene resin sheet of m was obtained. The operating conditions and the results are shown in Table 1.

Comparative Example 7 A sheet having a thickness of 0.3 m was prepared in the same manner as in Example 1 except that the temperature of the heating roll 10 was 165 ° C.
A polypropylene resin sheet of m was manufactured, but the sheet was fused to the metal belt 9. The operating conditions and the results are shown in Table 1.

Comparative Example 8 In Example 1, the clamping pressure using the hydraulic press 11 was applied.
A polypropylene resin sheet having a sheet thickness of 0.3 mm was obtained in the same manner as in Example 1 except that the treatment was performed at 3 kg / cm ² .
The operating conditions and the results are shown in Table 1.

Comparative Example 9 A sheet having a thickness of 0.3 mm was prepared in the same manner as in Example 1 except that the temperature of the heating roll 10 was 150 ° C.
A polypropylene resin sheet of was obtained. The operating conditions and the results are shown in Table 1.

EFFECTS OF THE INVENTION According to the improved water cooling method of the present invention, it is possible to obtain a sheet or film which is unoriented and has excellent transparency and surface gloss, using polypropylene resin as a raw material.

Moreover, even if the obtained sheet or film is thick, it has good transparency and surface gloss.

Further, according to the method of the present invention, a sheet or film having excellent transparency can be obtained even if the film forming speed is high.

Furthermore, the obtained sheet or film has no noticeable gel or fish eyes on the surface and is excellent in thermoformability.

Therefore, the sheet or film obtained by the method of the present invention is suitable for packaging foods, pharmaceuticals and the like. It can also be used as a raw material for thermoforming such as pressure forming.

[Brief description of drawings]

FIG. 1 is an explanatory view showing one mode of an apparatus for carrying out the method of the present invention. FIG. 2 is an explanatory view showing another embodiment of the apparatus for carrying out the method of the present invention. 1 ... T-die, 2 ... Membrane polypropylene resin, 3 ... Slit, 4 ... Upper water tank 4, 5 ... Lower water tank, 6 ... Clamping roll, 7 ... Take-up roll, 8 ... Polypropylene Resin sheet or film, 9 …… Metal belt, 10 …… Heating roll, 11 …… Hydraulic press, 12 …… Cooling roll, 13 …… Feeding device (feeding part of laminate material), 14 ……
Sheet or film.

Claims (1)

[Claims] 1. A sheet or film obtained by introducing a film-shaped polypropylene resin extruded in a molten state from a T-die into a slit through which cooling water flows and passing it through a pressure roll.
While heating to 155 to 160 ℃, with a metal belt with a surface roughness of 0.1 μm or less, 5 to 30 kg / c on both sides of the sheet or film.
A method for producing a polypropylene resin sheet or film, which comprises pressing at a pressure of m ² .